This invention relates to an apparatus and method for sorting waste which comprises materials having a low level of radioactivity.
Waste having low levels of radioactivity is created at nuclear power plants and similar facilities. Typically, waste comprises paper, fabrics, boots, clothing, tools and other items which can normally be expected to be used in the laboratories, offices, workshops and the like of a nuclear facility. Prior to its disposal the waste is taken through a series of inspections during which it is inspected for beta particle and gamma ray emissions.
To the extent that radioactive emissions above predetermined levels are detected, the waste is disposed of as hazardous by being buried at controlled disposal sites. Usually radiation in excess of 2 milliroentgens per hour is considered to be hazardous.
Waste which exhibits radiation which is less than 2 milliroentgens per hour is subjected to closer inspection in an attempt to remove its nonradioactive components so that they can be reused where appropriate or treated as ordinary non-hazardous waste. This reduces the volume of materials that must be buried at controlled sites and provides an opportunity to recover valuable items.
An aspect of inspecting waste relates to an inspection for low level beta particle emission and low level gamma ray emission. This is because a failure to detect and remove articles that are contaminated with low level radiation emitters could result in injury to persons who are exposed to the radiation over a long period of time. In order to minimize the radiation hazard to persons who are using the conveyor and apparatus of the present invention, the waste is given a preliminary examination so that items exhibiting relatively high levels of radioactivity, i.e., over 2 milliroentgens per hour are removed. Further means can be provided for subsequent examination of articles even if only very low levels of radiation are detected in order to assure that all contaminated articles are removed.
A process for the preliminary examination of radioactive waste of which the method and apparatus disclosed herein can be a part is disclosed in co-pending patent application Ser. No. 648,780 entitled METHOD FOR SORTING RADIOACTIVE WASTE which was filed by Alfred N. Johnson and Anthony J. Prisco on Sept. 10, 1984, and co-pending patent application Ser. No. 648,780 entitled METHOD AND APPARATUS FOR DETECTING RADIATION IN A CONTAINER which was filed by Alfred H. Johnson and Anthony J. Prisco on Sept. 10, 1984.
The apparatus disclosed herein is operative to provide a safe environment for technicians as waste which has been preliminarily sorted by the apparatus disclosed in U.S. Pat. No. 4,599,513, entitled ENCLOSURE FOR SORTING RADIOACTIVE MATERIAL is subjected to further examination in an attempt to locate articles which emit radioactivity and which have escaped detection in the aforementioned enclosure.